Humans only use 10% of their brain power

Science fiction loves the idea that there is untapped potential in the human brain, and that if we could just unlock it, we'd all make Einstein look like Joey Essex, intellectually speaking. Sadly this isn't the case, and while the brain is a hugely complex organ that can be trained to perform astonishing feats of data processing, it's actually exceptionally busy running the parts of the body we don't have to think about, so there's no secret door that will suddenly make you smarter.